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Linux kernel cgroups writeback high CPU troubleshooting
Read on to learn how we used network packet captures and BPF to debug web server performance, ultimately uncovering a Linux kernel performance issue. This investigation was a collaboration between myself and my colleagues.
The client waited over 1 second before sending the subsequent GET command, as if our PHP script stalled after the packet was received but before we recorded the elapsed time. Adding on to the evidence pointing away from network problems, we saw a large spike in system CPU usage about four minutes after newly autoscaled hosts were booted. We found that by creating a systemd slice with those controllers disabled and configuring setupwebroot ’s unit file to , we could no longer reproduce the elevated system CPU.
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